Phelps is a self-described "fire and brimstone" preacher who believes that homosexuality and its acceptance have doomed most of the world to eternal damnation. His group is estimated to number between 100-200 members (90 of whom are related to Phelps through blood or marriage). The group is built around an anti-homosexual core theology, with many of their activities stemming from the mantra "God hates fags," which is also the name of the group's webpage. Gay rights activists, as well as Christians of virtually every denomination, have denounced him as a producer of anti-gaypropaganda and violence-inspiring hate speech.

Phelps rose to national prominence in 1998 when he and congregants from Westboro picketed the funeral of gay murder victim Matthew Shepard, delivering an obscenity-laden sermon (with focus given to graphic descriptions of homosexual sex acts) informing the mourners that Shepard had gone to hell and that everyone in attendance would join him there. Ever since, Phelps and Westboro have remained in the national limelight for their regular pickets of events ranging from gay pride parades to the funerals of soldiers killed in the Iraq War to grand openings of Starbucks....

During 1993–94 interviews with the Topeka Capital-Journal, four of Phelps' children asserted that their father's religious beliefs were either nonexistent to begin with or have dwindled down to nearly nothing since his conversion to the Baptists; they claim that Westboro serves to enable a paraphilia of Phelps, wherein he is literally addicted to hatred (this statement would serve as the inspiration for the title of the book about Phelps' life). Two of his sons, Mark and Nate, claim that the church is actually a carefully planned cult that allows Phelps to see himself as a demigod, wielding absolute control over the lives of his family and congregants, essentially turning them into slaves that he can use for the sole purpose of gratifying his every whim and acting as the structure for his delusion that he is the only righteous man on Earth. [63] In 1995, Mark Phelps wrote a letter to the people of Topeka to this effect; it was run in the Topeka Capital-Journal. [64] The children's claim is partially backed up by B.H. McAllister, the Baptist minister who ordained Phelps. McAllister said in a 1993 interview that Phelps developed a delusion wherein he was one of the only people on Earth worthy of God's grace and that everyone else in the world was going to Hell, and that salvation or damnation could be directly obtained by either aligning with or opposing Phelps. Phelps maintains this belief to this day. [65]